The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structures.
In the past, the semiconductor industry utilized various methods and structures to build charge pump controllers that utilized capacitors to increase the value of a voltage from a voltage source in order to apply a large voltage to a load. Typically, transistors were used as switches that alternately coupled the pump capacitor to a voltage source for charging the pump capacitor and then coupled the pump capacitor in series with the voltage source to supply a higher voltage to the load. An example of a charge pump controller was disclosed in PCT patent publication No. WO/2007/008202 of inventor Remi Gerber that was published on Jan. 18, 2007.
When a switched capacitor controller first applied power to the pump capacitor, a large current was required to initially charge the capacitor to the desired voltage. This current was often referred to as an in-rush current. The in-rush current generally was very large and often exceeded the maximum current capacity of the voltage source used to charge the capacitor.
Also, if the output of the controller were shorted to ground, the short circuit condition often caused a large short-circuit current to flow which often damaged the controller.
Accordingly, it is desirable to have a switched capacitor controller that limits the value of the in-rush current and that minimizes damage under short-circuit conditions.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action. For clarity of the drawings, doped regions of device structures are illustrated as having generally straight line edges and precise angular corners. However, those skilled in the art understand that due to the diffusion and activation of dopants the edges of doped regions generally may not be straight lines and the corners may not be precise angles.
In addition, the device of the present invention will be illustrated to show either a cellular design (where the body regions of a transistor are a plurality of cellular regions) or a single body design (where the body region is comprised of a single region formed in an elongated pattern, typically in a serpentine pattern). The device of the present invention will be described as a single body design throughout the description for ease of understanding, however, it should be understood that it is intended that the present invention encompass both a cellular design and a single body design.